Computer network for calculating aircraft cornering friction based on data received from an aircraft&#39;s on board flight data management system

ABSTRACT

This invention relates to a computer network for calculating the true aircraft cornering friction coefficient of an aircraft runway or taxiway using the data collected by and available in the aircraft Flight Data Recorder (FDR) or other flight data management system, for example, the Quick Access Recorder (QAR). The invention may optionally distribute to personnel in the ground operations of an airport and airline operations, including but not limited to aircraft pilots, airline operation officers and airline managers as well as airport operators, managers and maintenance crews, the most accurate and most recent information concerning the true aircraft cornering friction coefficient to aid in making better and more accurate safety and economical decisions.

RELATED APPLICATION INFORMATION

This application is a continuation of co-pending U.S. application Ser.No. 13/694,866, filed Jan. 11, 2013, which, in turn, is a continuationof U.S. application Ser. No. 13/134,801, filed Jun. 17, 2011, now U.S.Pat. No. 8,355,850, issued Jan. 15, 2013, which in turn is acontinuation of U.S. application Ser. No. 12/802,066, filed May 28,2010, now abandoned, which, in turn, is a divisional of co-pending U.S.application Ser. No. 11/352,984, filed Feb. 13, 2006, now U.S. Pat. No.7,797,095, issued Sep. 14, 2010, which, in turn, claims the benefit ofand priority from U.S. provisional application No. 60/654,914, filedFeb. 23, 2005, now expired, all of the disclosures of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of invention

This invention relates to the method and the device of calculatingaircraft braking friction and other aircraft performance and pavementsurface characteristics parameters related to aircraft landing andtakeoff including but not limited to aircraft braking action, aircrafttakeoff distance, aircraft landing distance, runway surface conditionsand runway surface friction—from now on referred to as true aircraftlanding performance parameters—based on the data collected or otherwiseavailable on board of an aircraft in electronic or other format from theaircraft Flight Data Recorder (FDR) or any other flight data providingor management system for example the Quick Access Recorder (QAR).

2. Background

Under severe winter conditions airlines, airports, civil aviationorganizations and countries rigorously impose limits on aircrafttakeoff, landing and other surface movement operations as well asenforce weight penalties for aircraft takeoffs and landings. Theselimits depend on the weather, runway and taxiway surface conditions andaircraft braking and takeoff performance. At the present these limitsare calculated from the assumed aircraft braking performance based onrunway conditions. These conditions are established by visualinspections, weather reports and the measurements of runway frictioncoefficient using ground friction measurement equipment.

At the present time, there are several practices to calculate theassumed aircraft braking performance:

1. The Canadian CRFI method:

The CRFI method comprises a runway surface friction measurementperformed by braking a passenger vehicle traveling on the runway at acertain speed and measuring the maximum deceleration of it at severallocations along the length of the runway. The measured deceleration datais taken then and a braking index chart is used to calculate the assumedaircraft braking performance. The obtained aircraft landing performancedata and calculated assumed braking friction is provided to airlineoperators, pilots and airport personnel for decision making.

2. The reported runway friction coefficient by a runway frictionmeasurement equipment.

There are a great many number of runway friction measurement devicesmanufactured by different companies, in different countries and workingbased on different principles. Some of the most common devices are: (a)continuous friction measurement equipment (CFME); (b) decelerometers;and (c) side force friction coefficient measurement equipment. Thisequipment is operated by airport operation personnel according to themanufacturer's instructions on the runways, aprons, and taxiways and themeasured friction coefficient is recorded. The recorded frictioncoefficient is then distributed to airline operation personnel, pilots,and airport personnel. The measured coefficient of friction is dependenton the measurement device. Under the same conditions and on the samerunway different runway friction measurement devices based on differentprinciples will record different runway friction coefficients. Theserunway friction coefficients are assumed to relate to actual aircraftlanding and takeoff performance.

3. The new proposed IRFI method:

The International Runway Friction Index (IRFI) is a computational methodto harmonize the reported runway friction numbers reported by the manydifferent runway surface friction measurement equipments. The method wasdeveloped through an international effort with 14 participatingcountries. The method is a mathematical procedure based on simple linearcorrelations. The IRFI procedure is using a mathematical transformationto take the reported measurement of a runway friction measurement deviceand compute using simple mathematical methods an index called the IRFI.The mathematical procedures are the same for all the different runwayfriction measurement device using a different set of constant parametersthat was determined for each individual device. It is assumed that usingthis procedure the different runway friction measurement devicesreporting different friction coefficients can be harmonized. Thecalculated IRFI is assumed to correlate to aircraft landing and takeoffperformance.

4. Pre-determined friction levels based on observed runway conditions,current and forecasted weather conditions:

This method is available for airport operators according to newregulations. The method is based on airport personnel driving throughthe runway and personally observing the runway surface conditions. Theice, snow, water and other possible surface contaminants are visuallyobserved and their depth measured or estimated by visual observation.The estimated runway conditions with weather information are then usedto lookup runway friction coefficient in a table.

All these above mentioned practices are based on the measurement of therunway friction coefficient using ground friction measuring equipment,visual observation, weather information or combinations of these.However, according to present practices, there are several problems withthe measurement of the runway friction coefficient using these methods.

1. Need of a special device/car:

There is a special car needed to be able to measure the runway frictioncoefficient. There are special devices to measure the runway frictioncoefficient that are commercially available; however, most of thesedevices are very expensive. Therefore, not every airport can afford tohave one.

2. Close of runway:

For the duration of the measurement the runway has to be closed fortakeoffs and landings as well as any aircraft movement. The measurementof the runway surface friction takes a relatively large amount of timesince a measuring device has to travel the whole length of the runway ata minimum one time but during severe weather conditions it is possiblethat more than one measurement run is needed to determine runway surfacefriction. The closing of an active runway causes the suspension oftakeoff and landing aircraft operations for a lengthened period of timeand therefore is very costly for both the airlines and the airport. Theuse of ground vehicles to measure runway friction poses a safety hazardespecially under severe weather conditions.

3. Inaccurate result due to lack of maintenance and inaccuratecalibration level:

The result of the measurements are very dependent of the maintenance andthe calibration level of measurement devices, therefore the result canvary much, and could lose reliability.

4. Confusing results due to the differences between ground frictiondevices:

It has been established that the frictional values reported by differenttypes of ground friction measurement equipment are substantiallydifferent. In fact, the same type and manufacture, and even the samemodel of equipment frequently report highly scattered frictional data.Calibration and measurement procedures are different for different typesof devices. The repeatability and reproducibility scatter, or in otherwords, uncertainty of measurements for each type of ground frictionmeasurement device, is therefore amplified and the spread of frictionmeasurement values among different equipment types is significant.

5. Inaccurate result due to rapid weather change:

Airport operation personnel, in taking on the responsibility ofconducting friction measurements during winter storms, find it difficultto keep up with the rapid changes in the weather. During winter stormsrunway surface conditions can change very quickly and therefore frictionmeasurement results can become obsolete in a short amount of time, thusmisrepresenting landing and takeoff conditions.

6. Inaccurate result due to the difference between aircraft and theground equipment:

It is proven that the aircraft braking friction coefficients ofcontaminated runways are different for aircrafts compared to thosereported by the ground friction measurement equipment.

7. Inaccurate result due to the lack of uniform runway reportingpractices:

For many years the international aviation community has had no uniformrunway friction reporting practices. The equipment used and proceduresfollowed in taking friction measurements vary from country to country.Therefore, friction readings at various airports because of differencesin reporting practices may not be reliable enough to calculate aircraftbraking performance.

Therefore this invention recognizes the need for a system directlycapable of determining the true aircraft landing performance parametersbased on the data collected by and available in the aircraft Flight DataRecorder (FDR) or other flight data management systems. By utilizing thenovel method in this invention, for the first time all involvedpersonnel in the ground operations of an airport and airline operationsincluding but not limited to aircraft pilots, airline operation officersand airline managers as well as airport operators, managers andmaintenance crews, will have the most accurate and most recentinformation on runway surface friction and aircraft braking action,especially on winter contaminated and slippery runways.

Utilizing this method the aviation industry no longer has to rely ondifferent friction reading from different instrumentations and fromdifferent procedures.

Therefore, this method will represent a direct and substantial benefitfor the aviation industry.

BRIEF SUMMARY OF THE INVENTION Object of Invention

The objective of this invention is to provide all personnel involved inthe ground operations of an airport and involved in airline operationsincluding but not limited to aircraft pilots, airline operation officersand airline managers as well as airport operators, managers andmaintenance crews, the most accurate and most recent information on thetrue aircraft landing and takeoff performance parameters to help in abetter and more accurate safety and economical decision making, and toprevent any accident, therefore save lives.

Brief Summary of the Invention

This unique and novel invention is based on the fact that most modernairplanes throughout the entire flight including the takeoff and landingmeasures, collects and stores data on all substantial aircraft systemsincluding the braking hydraulics, speeds and hundreds of otherperformance parameters. During the landing maneuver real time or afterthe aircraft parked at the gate this data can be retrieved, processedand the true aircraft landing performance parameters can be calculated.

During a landing usually an aircraft uses its speed brakes, spoilers,flaps and hydraulic and mechanical braking system and other means todecelerate the aircraft to acceptable ground taxi speed. The performanceof these systems together with many physical parameters including butnot limited to various speeds, deceleration, temperatures, pressures,winds and other physical parameters are monitored, measured, collectedand stored in a data management system on board of the aircraft (FIG.1).

All monitored parameters can be fed real time into a high poweredcomputer system that is capable of processing the data and calculatingall relevant physical processes involved in the aircraft landingmaneuver. Based upon the calculated physical processes the actualeffective braking friction coefficient of the landing aircraft can becalculated. This, together with other parameters and weather data, canbe used to calculate the true aircraft landing performance parameters(FIG. 6).

If real time data processing is not chosen, then the collected data fromthe aircraft can be transported by wired, wireless or any other meansinto a central processing unit where the same calculation can beperformed (FIG. 8).

The obtained true aircraft landing performance parameters data then canbe distributed to all involved personnel in the ground operations of anairport and airline operations including but not limited to aircraftpilots, airline operation officers and airline managers as well asairport operators, managers and maintenance crews.

Utilizing the novel method in this invention for the first time allpersonnel involved in the ground operations of an airport and airlineoperations including but not limited to aircraft pilots, airlineoperation officers and airline managers as well as airport operators,managers and maintenance crews, will have the most accurate and mostrecent information on runway surface friction and aircraft brakingaction.

Utilizing this method, all the above mentioned (see BACKGROUND OF THEINVENTION) problems can be solved:

1. No need of a special device/car:

This method uses the airplane itself as measuring equipment, thereforeno additional equipment is needed. Moreover, no additional sensor isneeded. This method uses the readings of present sensors and otherreadily available data of an aircraft.

2. No need for closing of runway:

The duration of the measurement is the landing of the aircraft itself.Therefore the runway does not have to be closed.

3. No inaccurate result due to maintenance and the calibration level:

Because this method uses the aircraft itself as the measuring device,there is no variation due to the maintenance and the calibration levelof these ground friction measuring devices. The result of thecalculation will give back the exact aircraft braking friction theaircraft actually develops and encounters.

4. No inaccurate result due to the different between ground frictiondevices:

Because this method uses the aircraft itself as the measuring device,there is no variation due to the different ground friction measuringdevices.

5. Accurate result even in rapid weather change:

As long as aircraft are landing on the runway, the most accurate andmost recent information on the true aircraft landing performanceparameters will be provided by each landing.

6. No inaccurate result due to the difference between aircraft and theground equipment:

Because this method uses the aircraft itself as the measuring device,there is no discrepancy in the measured and real friction due to thedifference between aircraft and the ground equipment.

7. No inaccurate result due to the lack of uniform runway reportingpractices:

Because this method uses the aircraft itself as the measuring device,there is no variation due to the difference in reporting practices.

Utilizing this method the aviation industry no longer has to rely ondifferent friction readings from different instrumentations and fromdifferent procedures.

Therefore, this method represents a direct and substantial safety andeconomic benefits for the aviation industry.

The significance of this invention involves saving substantial amount ofmoney for the airline industry by preventing over usage of criticalparts and components of the aircraft, including but not limited tobrakes, hydraulics, and engines.

While increasing the safety level of the takeoffs, it could generatesubstantial revue for airlines by calculating the allowable take offweight, thus permissible cargo much more precisely.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a Flight Data Recorder illustrating the datacollection structure of the Flight Data Recorder of an aircraft.

FIG. 2 is a table illustrating data available from the Flight DataRecorder of a landing aircraft to reflect Pressure Altitude (in feet)versus time during a landing of the aircraft.

FIG. 3 is a table illustrating data available from the Flight DataRecorder of a landing aircraft to reflect Brake Pressure (in pounds persquare inch) versus Time during or landing of the aircraft.

FIG. 4 is a table illustrating data available from the Flight DataRecorder of a landing aircraft to reflect Autobrake Setting versus Timeduring landing of the aircraft.

FIG. 5 is a table illustrating a fraction of data available from aFlight Data Recorder.

FIG. 6 is a schematic flow chart illustrating the method of determiningvarious values generated by the present invention.

FIG. 7 is a table illustrating friction data indicative of limitedbraking plotting Mean Braking Pressure (in Pascals) versus Time (inSeconds) and illustrating corresponding Wheel Load and Wheel Friction.

FIG. 8 is a schematic illustrating transmission of data from a FlightData Management System of a landing aircraft for post processing anddistribution.

FIG. 9 is a schematic illustrating alternative real-time post processingand distribution and transmission of data from a Flight Data ManagementSystem of a landing aircraft.

DETAILED DESCRIPTION OF THE INVENTION

As illustrated in FIG. 1, this unique and novel invention is based onthe fact that every airplane during landing uses the hydraulics andbraking system. During a landing usually an aircraft uses its speedbrakes, spoilers, flaps and hydraulic and mechanic braking system andother means to decelerate the aircraft to acceptable ground taxi speed.The performance of these systems together with many physical parametersincluding but not limited to various speeds, deceleration, temperatures,pressures, winds and other physical parameters are monitored, measured,collected and stored in a data management system on board of theaircraft. This figure presents the schematics of the three majorcomponents of data sources onboard of an aircraft relevant to thisinvention, the measured and recorded parameters related to the brakingsystem, the measured and recorded parameters to the engines, flight andother control systems of the aircraft, and the dynamic, external andenvironmental parameters measured and recorded.

As illustrated in FIGS. 2 through 5, this invention uses the sequence ofdata points recorded from the touch down of the aircraft until itreaches the normal taxiing speed or comes to a stop. In the continuousdata stream of the flight data management system the touch down ismarked by several events making it possible to detect the beginning datapoint of the calculation process. From that point until the aircraftcomes to complete stop at the gate every necessary data points can beidentified within the recorded data. FIG. 2 shows the recorded altitudemeasurements for an actual landing FIG. 3 depicts the measured therecorded hydraulic braking pressures, FIG. 4 presents the recorded datafor the auto-brake selection and FIG. 5 illustrate the format of therecorded data that can be obtained form a digital flight data managementsystem.

As illustrated in FIG. 6, to arrive at the end result, a number ofdifferent mathematical and physical modeling approaches are possiblethrough different sets of dynamic equations and/or various methods ofsimulations based upon the availability of different sets of data fromthe flight data management system.

The following equations only represent an example of the possibleapproaches, and therefore the invention and the presented method is notlimited to these equations.

6.1—The following data is used as one of the possible minimum data setsfor the calculation, although more and/or different data can be utilizedto calculate the same parameters and/or improve the precision of thecalculation.

Data from the Flight Data Recorder:

V_(air) Air Speed, P_(LB), P_(RB) Left and Right Brake Pressure, V_(g)Ground Speed, A_(x) Longitudinal Acceleration, A_(c) VerticalAcceleration, E_(RPM) Engine RPM, S_(spolier) Spoiler setting,S_(airbrake) Airbrake setting, S_(aileron) Aileron setting, C_(flap)Flap configuration, θ_(pitch) Pitch, S_(RT) Reverse thrust setting,S_(T) Engine thrust setting

The following environmental data are used in the calculation.

T_(air) Air Temp, P_(alt) Pressure Altitude, P_(air) Air Pressure, H_(%)Relative humidity, Δ_(Runway) Runway elevation

The following aircraft parameters are used in the calculation.

M_(landing) Landing Mass, E_(type) Engine type, N_(engine) Number ofengines, TY_(tire) Tire type, TY_(aircraft) Aircraft type

6.2—The method calculates, through a three-dimensional dynamic model,all relevant physical processes involved in the aircraft landingmaneuver and separates them so they are individually available for use.The first intermediate result of the method is the time or distancehistory of all relevant, separated, interdependent decelerationsgenerated by the different systems in an aircraft. These decelerationsare cumulatively measured by the onboard measurement system and reportedin the flight data stream. The separated decelerations calculated fromthe different physical processes make it possible to calculate the truedeceleration developed only by the actual effective braking frictioncoefficient of the landing aircraft.

Based on the above, the software calculates the brake effectiveacceleration vs. time based on Equation (1).

A _(Be) =A _(x) −A _(Drag) −A _(ReverseThrust) −A _(Rolling Resistance)−A _(Pitch)   (1)

where A_(Be) is the brake effective acceleration

-   -   A_(x) is the measured cumulative longitudinal acceleration (6.1)    -   A_(Drag) is the deceleration due to the aerodynamic drag,

A _(Drag) =f(V _(air) ,S _(spoiler) ,S _(airbrake) ,S _(aileron) ,C_(flap) ,T _(air) ,P _(air) ,H _(%) ,M _(landing) ,TY _(aircraft))   (2)$

-   -   -   where            V_(air),S_(spoiler),S_(airbrake),S_(aileron),C_(flap),T_(air),P_(air),H_(%),M_(landing),TY_(aircraft)            are parameters from 6.1.

    -   A_(ReverseThrust) is the acceleration caused by        thrust/reverse-thrust

A _(ReverseThrust) =f(E _(type) ,N _(engine) ,T _(air) ,P _(air) ,H _(%),E _(RPM) ,S _(RT) ,M _(landing) ,TY _(aircraft))   (3)

-   -   -   where            E_(type),N_(engine),T_(air),P_(air),H_(%),E_(RPM),S_(RT),M_(landing);TY_(aircraft)            are parameters from 6.1

    -   A_(RollingResistance) is the cumulative deceleration due to        other effects such as tire rolling resistance, runway        longitudinal elevation

A _(Rolling Resistance) =f(tire,V _(g) ,M _(landing))   (4)

-   -   -   where tire,V_(g),M_(landing) are parameters from 6.1

    -   A_(Pitch) is due to the runway elevation

A _(Pitch) =f(Δ_(Runway))   (5)

-   -   -   where Δ_(Runway) is the runway elevation from 6.1.

This true deceleration (A_(Be)) developed only by the actual effectivebraking friction coefficient of the landing aircraft, then can be usedin further calculations to determine the true aircraft brakingcoefficient of friction.

6.3—Using the recorded data stream of the aircraft with the parametersindicated in point 6.1, plus weather and environmental factors reportedby the airport or measured onboard of the aircraft and thereforeavailable in the recorded data, together with known performance anddesign parameters of the aircraft available from design documentationand in the literature, the dynamic model calculates all relevant actualforces acting on the aircraft as a function of the true ground and airspeeds, travel distance and time. Using the results, the dynamic wheelloads of all main gears and the nose gear can be calculated.

Since the dynamic vertical acceleration of the aircraft is measured bythe onboard inertial instrumentation, the effective dynamic wheel load(N) can be calculated by the deduction of the calculated retardingforces by means of known aircraft mass; together with the determinedgravitational measurement biases introduced by runway geometry andaircraft physics using Equations 6 through 9.

N=M _(Landing)·cos(θ_(pitch))·g−Lift−LoadTransfer−MomentumLift+g(A _(c),M _(landing))   (6)

Where

-   -   Lift is the computed force of the sum of all lifting forces        acting on the aircraft through aerodynamics:

Lift=f(V _(air) ,S _(spoiler) ,S _(airbrake) ,S _(aileron) ,C _(flap) ,T_(air) ,P _(air) ,H _(%) ,M _(landing) ,TY _(aircraft))   (7)

-   -   -   where            V_(air),S_(spoiler),S_(airbrake),S_(aileron),C_(flap),T_(air),P_(air),H_(%),M_(landing),TY_(aircraft)            are parameters from point 6.1.

    -   LoadTransfer is the load transfer from the main landing gear to        the nose gear due to the deceleration of the aircraft:

LoadTransfer=f(A _(Be) ,M _(landing) ,TY _(aircraft))   (8)

-   -   -   where A_(Be),M_(landing),TY_(aircraft) parameters from 6.1.

    -   MomentumLift is the generated loading or lifting forces produced        by moments acting on the aircraft body due to the acting points        of lift, thrust and reverse-thrust forces on the aircraft        geometry:

MomentumLift=f(S _(Thrust) ,S _(RT) ,C _(flap) ,TY _(aircraft))   (9)

-   -   -   where S_(Thrust),S_(RT),C_(flap),TY_(aircraft) are            parameters from point 6.1

    -   g(A_(c), M_(landing)) is the dynamic force acting on the landing        gear due to the dynamic vertical movement of the aircraft, and        thus the varying load on the main gear due to the runway        roughness,        -   where A_(c), M_(landing) are parameters from point 6.1.

6.4—The deceleration caused by the wheel braking system of the aircraftcalculated in point 6.2 (A_(Be) is the true brake effectivedeceleration), together with the computed actual wheel load forcesacting on the main gears of the aircraft can be used to calculate thetrue braking coefficient of friction. First the actual true decelerationforce or friction force (F_(Fr)) caused by the effective braking of theaircraft have to be computed. From the brake effective deceleration(A_(Be)) obtained in 6.2 and the available aircraft mass, the methodcalculates the true effective friction force based on the formula:

F _(Fr) =M _(landing) ·A _(Be)   (10)

where M_(landing) is the landing mass of the aircraft from point 6.1 andA_(Be) is the calculated brake effective deceleration from Equation (1).

The determined true deceleration force (F_(Fr)) in equation 10 togetherwith the actual effective dynamic wheel load (N) obtained in 6.3 can beutilized to calculate the true effective braking coefficient of frictionμ using equation 11:

μ=F _(Fr) /N   (11)

where

-   -   N is the calculated effective dynamic wheel force acting on the        tire (6.3),    -   and F_(Fr) is the friction force from Equation (10).

6.5—Using the calculated effective true frictional forces, together withparameters measured by the aircraft data management system (such asdownstream hydraulic braking pressure), a logical algorithm based on thephysics of the braking of pneumatic tires with antiskid braking systemswas designed to determine whether the maximum available runway frictionwas reached within the relevant speed ranges of the landing maneuver.

Together with the actual friction force the following logic is used bythis invention to determine:

(A) If friction limited braking is encountered—If the actual availablemaximum braking friction available for the aircraft was reached by thebraking system and even though more retardation was needed the brakingsystem could not generate because of the insufficient amount of runwaysurface friction a friction limited braking was encountered.

(B) If adequate friction for the braking maneuver was available—Iffriction limited braking was not encountered and the braking was limitedby manual braking or the preset level of the auto-brake system, theadequate surface friction and actual friction coefficient can becalculated and verified.

6.6—In order to make sure that the auto-brake and antiskid systems ofthe aircraft were working in their operational range, the algorithmanalyzes the data to look for the friction limited sections only in anoperational window where the landing speed is between 20 m/s and 60 m/s.

6.7—From the computed true effective braking coefficient of friction μcalculated in 6.4, the method computes the theoretically necessaryhydraulic brake pressure P_(brake) and from the dynamics of the landingparameters an applicable tolerance is calculated t.

6.8—The data is analyzed for the deviation of the applied downstreamhydraulic brake pressure from the calculated theoretical brake pressurefrom 6.7 according to the obtained effective braking friction within theallowed operational window by the determined t tolerance. A sharpdeviation of the achieved and the calculated hydraulic braking pressureis the indication of friction limited braking. When sharply increasedhydraulic pressure is applied by the braking system, while nosignificant friction increase is generated, the potential of truefriction limited braking occurs.

FIG. 7 illustrates a graphical presentation for an example for thefriction limited braking, where it can be seen that that a sharplyincreasing hydraulic pressure is applied by the braking system, whilethe friction is decreasing. This is a very good example for a truefriction limited braking.

The Different Applications of this Method

The Post Processing

FIG. 8 illustrates one possible approach in obtaining the true aircraftlanding performance parameters is a method of post processing. The datafrom the aircraft flight data management system is retrieved not realtime but only after the aircraft is finished its landing, taxiing andother ground maneuvers and arrived at its final ground position. Theschematic of this approach is described in FIG. 8.

8.1—All monitored and available data is sent to the flight datamanagement system throughout the aircraft landing and ground maneuver.

8.2—The Flight Data Management system collects, processes and stores theretrieved data in a data storage. The data storage is in fact part ofthe Flight Data Management system where all the data is stored.

8.3—Data transfer—After the airplane stopped at the gate or otherdesignated final position, the collected data from the aircraft can betransported by wired, wireless or other means into a central processingunit.

8.4—High Power computer—All recorded parameters transported from theaircraft can be fed into a computer system, which is capable ofprocessing the data and calculating/simulating all relevant physicalprocesses involved in the aircraft landing maneuver and the actualeffective braking friction coefficient of the landing aircraft and thetrue aircraft landing performance parameters can be computed and madeready for distribution.

8.5—Data Distribution—The computer distributes the calculated truelanding parameters to other interested parties through wired, wirelessor other data transportation means.

Real-Time Data Processing

As illustrated in FIG. 9, in the case of real time data processing, allmonitored parameters can be fed real time into an onboard high powercomputer system that is capable of processing the data and calculatingall relevant physical processes involved in the aircraft landingmaneuver. Based upon the calculated physical processes the actualeffective braking friction coefficient of the landing aircraft can becalculated. This together with other parameters and weather data can beused to calculate the true aircraft landing performance parameters. Incase the calculation finds a true friction limited section, a warningcan be sent to the pilot to prevent any accident, such as over run orslide off the runway.

9.1—All monitored and available data is sent to the flight datamanagement system throughout the aircraft landing and ground maneuver.

9.2—The Flight Data Management system collects, processes and stores theretrieved data in a data storage. The data storage is in fact part ofthe Flight Data Management system where all the data is stored.

9.3—High power computer system: All monitored parameters are fed realtime into a computer system, which is capable of processing the data andcalculating/simulating all relevant physical processes involved in theaircraft landing maneuver and the actual effective braking frictioncoefficient of the landing aircraft and the true aircraft landingperformance parameters.

9.4—Pilot warning: Based on the calculated aircraft braking coefficientand the method to search for friction limited braking it gives a warningin case the friction is too low or continuously informs the driver ofthe generated and available braking and cornering coefficient offriction.

9.5—Distribution: The onboard computer distributes the calculated truelanding parameters to other interested parties.

Significance of the Invention

Utilizing the novel method in this invention for the first time allpersonnel involved in the ground operations of an airport as well asairline personnel involved in operations including but not limited toaircraft pilots, airline operation officers and airline managers as wellas airport operators, managers and maintenance crews, will have the mostaccurate and most recent information on runway surface friction andaircraft braking action.

Utilizing this method the aviation industry no longer has to rely ondifferent friction readings from different instrumentations and fromdifferent procedures or assumed friction levels based on visualobservation and weather data.

Therefore, this method represents a direct and substantial safety andeconomic benefits for the aviation industry.

Economic Benefits

The significance of this invention involves knowing the true aircraftlanding performance parameters for landing which yields substantialfinancial savings for the airline industry. While increasing the safetylevel of the takeoffs, it could also generate substantial revenue forairlines.

Therefore a system directly capable of determining the true aircraftlanding performance parameters would represent direct and substantialeconomic benefit for the aviation industry including but not limited to:

-   -   1. Preventing over usage of critical parts, components of the        aircraft including but not limited to brakes, hydraulics, and        engines.    -   2. The distribution of the calculated parameters for the airport        management helps make more accurate, timely and economic        decisions including but not limited to decision on closing the        airport or decision on the necessary maintenance.    -   3. The calculated parameters reported to the airline management        yields more accurate and economic decision making including but        not limited to permitting the calculation of allowable take off        weights much more precisely thus increasing the permissible        cargo limits.

Safety Benefits

The significance of this invention involves the precise assessment ofthe true runway surface characteristics and aircraft braking and landingperformance by providing the true aircraft landing performanceparameters. This is fundamental to airport aviation safety, andeconomical operations especially under winter conditions and slipperyrunways. Thus, a system directly capable of determining the trueaircraft landing performance parameters real-time and under anyconditions without restricting ground operations of an airport wouldrepresent direct and substantial safety benefit for the aviationindustry including but not limited to:

-   -   1. Providing real-time low friction warning to help pilots to        make critical decisions during landing or take-off operations to        prevent accidents, costly damages or loss of human lives.    -   2. Eliminating the confusion in the interpretation of the        different Ground Friction Measuring Device readings and        therefore giving precise data to airport personnel for critical        and economical decision making in airport operations and        maintenance.    -   3. Giving an accurate assessment of the actual surface        conditions of the runway, that could be used in the aircraft        cargo's loading decision making for safer landing or take-offs.    -   4. Providing accurate data for distribution to airport        management personnel assisting them in more accurate, timely and        safe decision making.    -   5. Providing data to be reported to pilots about to land for        safer and more accurate landing preparation.    -   6. Providing data to be reported to pilots about to take off for        safer and more accurate takeoff preparation.    -   7. It could be reported to the airline management to for more        accurate safety decision making.

I claim:
 1. A computer network for calculating and distributing a trueaircraft cornering friction coefficient of an aircraft runway oraircraft taxiway, comprising: (A) A computer for obtaining aircraftproperty data directly or indirectly from a flight data managementsystem of an aircraft, wherein the aircraft property data comprises datapertaining to one or more of the following aircraft properties measuredat various times for the aircraft and recorded on the aircraft's flightdata management system: aircraft ground speed, aircraft brake pressure,aircraft longitudinal acceleration, aircraft engine thrust setting,aircraft reverse thrust setting, aircraft engine revolutions per minute,aircraft air speed, aircraft vertical acceleration, aircraft spoilersetting, aircraft airbrake setting, aircraft aileron setting, aircraftflap configuration, aircraft pitch, and aircraft autobrake setting; (B)Wherein the computer obtains at least some of the aircraft property datadirectly or indirectly from the aircraft's flight data managementsystem; and (C) Wherein the computer calculates the true aircraftcornering friction coefficient of the aircraft runway or aircrafttaxiway using at least some of the aircraft property data.
 2. Thecomputer network for calculating and distributing the true aircraftcornering friction coefficient of the aircraft runway or aircrafttaxiway of claim 1 wherein the computer is located on the aircraft. 3.The computer network for calculating and distributing the true aircraftcornering friction coefficient of the aircraft runway or aircrafttaxiway of claim 1: (A) Wherein the computer obtains environmentalparameter data directly or indirectly from one or more sources of one ormore environmental parameters chosen from the following group: airtemperature, air pressure, relative humidity, wind speed, winddirection, pressure altitude, and aircraft surface elevation; and (B)Wherein the computer calculates the true aircraft cornering frictioncoefficient of the aircraft runway or aircraft taxiway using at leastsome of the environmental parameter data.
 4. The computer network forcalculating and distributing the true aircraft cornering frictioncoefficient of the aircraft runway or aircraft taxiway of claim 2: (A)Wherein the computer obtains environmental parameter data directly orindirectly from one or more sources of one or more environmentalparameters chosen from the following group: air temperature, airpressure, relative humidity, wind speed, wind direction, pressurealtitude, and aircraft surface elevation; and (B) Wherein the computercalculates the true aircraft cornering friction coefficient of theaircraft runway or aircraft taxiway using at least some of theenvironmental parameter data.
 5. The computer network for calculatingand distributing the true aircraft cornering friction coefficient of theaircraft runway or aircraft taxiway of claim 1: (A) Wherein the computerobtains aircraft parameter data directly or indirectly from one or moresources of one or more aircraft parameters pertaining to the aircraftchosen from the following group: aircraft landing mass, aircraft enginetype, number of aircraft engines, aircraft tire type, and aircraft type;and (B) Wherein the computer calculates the true aircraft corneringfriction coefficient of the aircraft runway or taxiway using at leastsome of the aircraft parameter data.
 6. The computer network forcalculating and distributing the true aircraft cornering frictioncoefficient of the aircraft runway or aircraft taxiway of claim 2: (A)Wherein the computer obtains at least some of the aircraft parameterdata directly or indirectly from one or more sources of one or moreaircraft parameters pertaining to the aircraft chosen from the followinggroup: aircraft landing mass, aircraft engine type, number of aircraftengines, aircraft tire type, and aircraft type; and (B) Wherein thecomputer calculates the true aircraft cornering friction coefficient ofthe aircraft runway or taxiway using at least some of the aircraftparameter data.
 7. The computer network for calculating and distributingthe true aircraft cornering friction coefficient of the aircraft runwayor aircraft taxiway of claim 3: (A) Wherein the computer obtainsaircraft parameter data directly or indirectly from one or more sourcesof one or more aircraft parameters pertaining to the aircraft chosenfrom the following group: aircraft landing mass, aircraft engine type,number of aircraft engines, aircraft tire type, and aircraft type; and(B) Wherein the computer calculates the true aircraft cornering frictioncoefficient of the aircraft runway or taxiway using at least some of theaircraft parameter data.
 8. The computer network for calculating anddistributing the true aircraft cornering friction coefficient of theaircraft runway or aircraft taxiway of claim 4: (A) Wherein the computerobtains aircraft parameter data directly or indirectly from one or moresources of one or more aircraft parameters pertaining to the aircraftchosen from the following group: aircraft landing mass, aircraft enginetype, number of aircraft engines, aircraft tire type, and aircraft type;and (B) Wherein the computer calculates the true aircraft corneringfriction coefficient of the aircraft runway or taxiway using at leastsome of the aircraft parameter data.
 9. The computer network forcalculating and distributing the true aircraft cornering frictioncoefficient of the aircraft runway or taxiway of claim 1, wherein thecomputer directly or indirectly provides one or more of the followingindividuals or entities with the true aircraft cornering frictioncoefficient calculated by the computer: airline operation personnel,pilots, airport personnel, airline managers, airport managers, airportmaintenance crews, pilots of aircraft scheduled to take off, land, ortaxi on the aircraft runway or taxiway, personnel involved in groundoperations where the aircraft runway or taxiway is located, aircraftscheduling and dispatch personnel, flight service center personnel,government aviation authority personnel, air traffic controllers,airline employees, and aircraft manufacturers.
 10. The computer networkfor calculating and distributing the true aircraft cornering frictioncoefficient of the aircraft runway or taxiway of claim 2, wherein thecomputer directly or indirectly provides one or more of the followingindividuals or entities with the true aircraft cornering frictioncoefficient calculated by the computer: airline operation personnel,pilots, airport personnel, airline managers, airport managers, airportmaintenance crews, pilots of aircraft scheduled to take off, land, ortaxi on the aircraft runway or taxiway, personnel involved in groundoperations where the aircraft runway or taxiway is located, aircraftscheduling and dispatch personnel, flight service center personnel,government aviation authority personnel, air traffic controllers,airline employees, and aircraft manufacturers.
 11. The computer networkfor calculating and distributing the true aircraft cornering frictioncoefficient of the aircraft runway or taxiway of claim 3, wherein thecomputer directly or indirectly provides one or more of the followingindividuals or entities with the true aircraft cornering frictioncoefficient calculated by the computer: airline operation personnel,pilots, airport personnel, airline managers, airport managers, airportmaintenance crews, pilots of aircraft scheduled to take off, land, ortaxi on the aircraft runway or taxiway, personnel involved in groundoperations where the aircraft runway or taxiway is located, aircraftscheduling and dispatch personnel, flight service center personnel,government aviation authority personnel, air traffic controllers,airline employees, and aircraft manufacturers.
 12. The computer networkfor calculating and distributing the true aircraft cornering frictioncoefficient of the aircraft runway or taxiway of claim 4, wherein thecomputer directly or indirectly provides one or more of the followingindividuals or entities with the true aircraft cornering frictioncoefficient calculated by the computer: airline operation personnel,pilots, airport personnel, airline managers, airport managers, airportmaintenance crews, pilots of aircraft scheduled to take off, land, ortaxi on the aircraft runway or taxiway, personnel involved in groundoperations where the aircraft runway or taxiway is located, aircraftscheduling and dispatch personnel, flight service center personnel,government aviation authority personnel, air traffic controllers,airline employees, and aircraft manufacturers.
 13. The computer networkfor calculating and distributing the true aircraft cornering frictioncoefficient of the aircraft runway or taxiway of claim 5, wherein thecomputer directly or indirectly provides one or more of the followingindividuals or entities with the true aircraft cornering frictioncoefficient calculated by the computer: airline operation personnel,pilots, airport personnel, airline managers, airport managers, airportmaintenance crews, pilots of aircraft scheduled to take off, land, ortaxi on the aircraft runway or taxiway, personnel involved in groundoperations where the aircraft runway or taxiway is located, aircraftscheduling and dispatch personnel, flight service center personnel,government aviation authority personnel, air traffic controllers,airline employees, and aircraft manufacturers.
 14. The computer networkfor calculating and distributing the true aircraft cornering frictioncoefficient of the aircraft runway or taxiway of claim 7, wherein thecomputer directly or indirectly provides one or more of the followingindividuals or entities with the true aircraft cornering frictioncoefficient calculated by the computer: airline operation personnel,pilots, airport personnel, airline managers, airport managers, airportmaintenance crews, pilots of aircraft scheduled to take off, land, ortaxi on the aircraft runway or taxiway, personnel involved in groundoperations where the aircraft runway or taxiway is located, aircraftscheduling and dispatch personnel, flight service center personnel,government aviation authority personnel, air traffic controllers,airline employees, and aircraft manufacturers.
 15. The computer networkfor calculating and distributing the true aircraft cornering frictioncoefficient of the aircraft runway or taxiway of claim 1 wherein atleast some of the aircraft property data recorded on the flight datamanagement system is measured substantially at or after the time whenthe aircraft touches down on the aircraft runway during landing.
 16. Thecomputer network for calculating and distributing the true aircraftcornering friction coefficient of the aircraft runway or taxiway ofclaim 15 wherein at least some of the aircraft property data recorded onthe flight data management system is measured substantially before oruntil the aircraft completes taxiing following landing.
 17. The computernetwork for calculating and distributing the true aircraft corneringfriction coefficient of the aircraft runway or taxiway of claim 3wherein at least some of the aircraft property data recorded on theflight data management system is measured substantially at or after thetime when the aircraft touches down on the aircraft runway duringlanding.
 18. The computer network for calculating and distributing thetrue aircraft cornering friction coefficient of the aircraft runway ortaxiway of claim 17 wherein at least some of the aircraft property datarecorded on the flight data management system is measured substantiallybefore or until the aircraft completes taxiing following landing. 19.The computer network for calculating and distributing the true aircraftcornering friction coefficient of the aircraft runway or taxiway ofclaim 3 wherein at least some of the environmental parameter data ismeasured substantially in the vicinity of the aircraft.
 20. The computernetwork for calculating and distributing the true aircraft corneringfriction coefficient of the aircraft runway or taxiway of claim 4wherein at least some of the environmental parameter data is measuredsubstantially in the vicinity of the aircraft.
 21. The computer networkfor calculating and distributing the true aircraft cornering frictioncoefficient of the aircraft runway or aircraft taxiway of claim 13wherein the computer is located on the aircraft.
 22. The computernetwork for calculating and distributing the true aircraft corneringfriction coefficient of the aircraft runway or aircraft taxiway of claim14 wherein the computer is located on the aircraft.
 23. The computernetwork for calculating and distributing the true aircraft corneringfriction coefficient of the aircraft runway or aircraft taxiway of claim15 wherein the computer is located on the aircraft.
 24. The computernetwork for calculating and distributing the true aircraft corneringfriction coefficient of the aircraft runway or aircraft taxiway of claim16 wherein the computer is located on the aircraft.
 25. The computernetwork for calculating and distributing the true aircraft corneringfriction coefficient of the aircraft runway or aircraft taxiway of claim17 wherein the computer is located on the aircraft.
 26. The computernetwork for calculating and distributing the true aircraft corneringfriction coefficient of the aircraft runway or aircraft taxiway of claim18 wherein the computer is located on the aircraft.